Coaxial or dual containment piping systems may be utilized in systems in which fuel or other environmentally sensitive fluids are stored and/or transported. Such dual containment systems are often utilized at refueling stations, such as gas stations, but can be used in a variety of other settings as well. In such a system, the inner, or primary, pipe is designed to carry the fluid, and an outer, or secondary, pipe is positioned about the primary pipe to provide secondary containment to the primary pipe. In some systems the pressure of the interstitial space between the primary and secondary pipes is monitored such that any leaks or integrity losses may be able to be detected by a change in interstitial pressure.
Couplings in dual containment systems can be difficult to implement since it is desired to maintain the integrity of the primary pipe, secondary pipe, and interstitial space. In such cases transition couplings may be used when it is desired to preserve the interstitial pressure of the piping system, or communicate the interstitial pressure to a remote location. For example, transition couplings may be utilized at T-fittings, elbow fittings, straight connections or fittings, sump connections, at a terminus of the pipe system, etc. However, existing transition couplings can be difficult to install, and may not provide sufficient sealing characteristics.